Strontium chloride

Endpoint summary

Additional information

Read-across statement:

No or few ecotoxicological data are available for strontium chloride itself. For metals it is generally assumed that toxicity is controlled by the dissolved metal ion. The speciation and chemistry of strontium is rather simple. As a reactive electropositive metal, strontium is easily oxidized to the stable and colourlessSr²⁺ion in most of its compounds, the chemical behaviour resembling that of Ca and/or Ba (Wennig and Kirsch, 1988). In the environment, the element only occurs in one valence state (Sr²⁺), does not form strong organic or inorganic complexes and is commonly present in solution asSr²⁺(Lollar, 2005). Consequently, the toxicity of strontium in the environment is largely controlled by solubility of different Sr-salts (SrCO₃,Sr(NO₃)₂,SrSO₄,Sr(OH)₂…)

 

These findings are sufficient justification for the implementation of a read-across strategy with ecotoxicity results obtained in tests that were conducted with different strontium compounds that generate freeSr²⁺-ions in solution, and this for all relevant environmental endpoints that were considered.

Short-term toxicity data

Reliable acute data are available for three trophic levels: algae, invertebrates and fish.

·        An unbounded value of >43.3 mg Sr/L was identified for algae.

·        The only bounded acute value of 125 mg Sr/L is available for the invertebrate D. magna.

·        The lowest acute effect value (based on measured Sr in the test medium) was an unbounded value of >40.3 mg Sr/L for the fishC. carpio.

It should be noted that the actual E(L)C₅₀values for fish and algae may be well above the reported values as not even partial effects (i.e., mortality or growth rate inhibition) were noted at the highest test concentrations.The table below provides an overview of the most sensitive, reliable, short-term toxicity freshwater data available for strontium.

Table: Most sensitive reliable short-term toxicity endpoints for strontium in freshwater

Species	Parameter	Endpoint	Value (mg Sr/L)	Reference
Acute fish data
Cyprinus carpio	mortality	96h-LC50	> 40.3	Tobor-Kaplon (2010)
Acute invertebrate data
Daphnia magna	mortality/immobility	48h-LC50	125	Biesinger and Christensen (1972)
Algal data
Pseudokirchneriella subcapitata	growth rate	72h-ErC50	> 43.3	Tobor-Kaplon (2010)

 

Long-term toxicity data

Reliable studies on chronic toxicity of strontium to the aquatic environment are available for three trophic levels: algae, invertebrates and fish. The toxicity tests were performed using strontium nitrate or strontium chloride hexahydrate as test substance.

 ·        In the study of growth inhibition of the algal species Pseudokirchneriella subcapitataby strontium nitrate to, all significant effect levels (acute and chronic) were equal or higher than 43.3 mg Sr/L (conservative value). Thus, the 72-h NOEC is ≥ 43.3 mg Sr/L.

·        The study on the chronic toxicity of strontium to invertebrates (Biesinger and Christensen, 1972) reported a calculated NOEC forDaphnia magna(i.e., EC₁₆/2) of 21 mg Sr/L.

·        A chronic fish study according to OECD 210 (Egeler and Morlock, 2013) was performed with Danio rerio. The NOEC (nominal) was set to ≥100 mg/L for strontium nitrate, corresponding to a re-calculated NOEC (nominal) for strontium of ≥ 41.4 mg/L.

 

The PNEC_aquaticcalculation will be conducted using the assessment factors method since a large dataset from long-term tests for different taxonomic groups is not available, a Species Sensitivity Distribution (SSD) cannot be developed and statistical extrapolation methods can thus not be used to derive the PNEC_aquatic. An overview of available long-term data used for PNEC-derivation is provided in the Table below.

Table: Most sensitive reliable long-term toxicity data for strontium in freshwater

Species	Parameter	Endpoint	Value (mg Sr/L)	Reference
Danio rerio	mortality	34d-NOEC	≥ 41.4	Egeler and Morlock (2013)
Pseudokirchneriella subcapitata		72-h NOECr	≥ 43.3	Tobor-Kaplon (2010)
Daphnia magna	mortality	21d-NOEC	21	Biesinger and Christensen (1972)